Daemonosaurus

This site, preserving the informal late Norian or Rhaetian "siltstone member" of the Chinle Formation, is famous for abundant fossils of Coelophysis, an early theropod.

The specific name is derived from the Greek word "chauliodous" (χαυλιόδους) meaning "prominent toothed", which is in reference to its procumbent front teeth.

[1] Daemonosaurus is notable for its short, deep skull, with large teeth, a rounded orbit (eye socket) and a relatively small antorbital fenestra.

The proportionately large orbit, the short snout, and the apparent lack of fusion between the bones of the braincase suggest that the holotype specimen CM 76821 may be a juvenile.

Similar to many early dinosaurs, a small diastema (toothless notch) was present at the lower contact between the premaxilla and maxilla.

Like Tawa and Herrerasaurus, the outer surface of the maxilla is generally smooth and flat; there are no sharp ridges delimiting the tooth row or the shallow, upwards-oriented antorbital fossa.

Their rear edge is excavated by the supratemporal fossa, which extends onto the broad and mostly flat parietal, as well as the fairly large postorbital.

The postorbital likely contacted the frontal along a straight edge (like Tawa and Herrerasaurus), while also sending a rounded overhanging projection into the orbit (like most early saurischians).

[1] With such a basal position, Daemonosaurus represents a lineage that extended from the earliest radiation of dinosaurs in the Middle Triassic alongside forms such as Eoraptor and Herrerasaurus from South America.

A phylogenetic analysis conducted in its original description found Daemonosaurus chauliodus to be closely related to Tawa hallae, a theropod that was described from Ghost Ranch in 2009, and the Neotheropoda.

Sues et al. (2011) noted that the discovery of Daemonosaurus provided "additional support for the theropod affinities of both Eoraptor and Herrerasauridae and (demonstrated) that lineages from the initial radiation of Dinosauria persisted until the end of the Triassic."

Daemonosaurus differs from Eoraptor lunensis based on the presence of much larger premaxillary and anterior maxillary teeth and a much more restricted antorbital fossa on the maxilla.

A paper published by Baron et al. (2017) resurrected the clade Ornithoscelida to unite ornithischians and theropods to the exception of sauropodomorphs.

[6] Although not included in the original study, the authors added Daemonosaurus to their dataset after their hypothesis was criticized by a team of international researchers, Langer et al.

When Agnosphitys (a fragmentary possible silesaurid) was removed from the analysis, Daemonosaurus was placed as the sister taxon to Eusaurischia, which encompassed the theropod-sauropodomorph split.

Though Nesbitt and Sues (2020) considered Daemonosaurus a likely saurischian, they were unable to conclusively place the genus within any subgroup of Dinosauria.

This site preserves pebbly, calcareous conglomerate rich in fossils of many different animals, with the theropod dinosaur Coelophysis being particularly abundant.

It has been correlated the Siltstone Member of the Chinle Formation, which is tentatively dated to the Rhaetian (or possibly latest Norian) stage of the Late Triassic period.

[1][2] Ghost Ranch was located close to the equator 200 million years ago, and had a warm, monsoon-like climate with heavy seasonal precipitation.

Archosauriform taxa present include phytosaurs (Redondasaurus), crocodylomorphs (Hesperosuchus), shuvosaurids (Effigia), the silesaurid Eucoelophysis, and the dinosaur Coelophysis.

The Whitaker Quarry of Ghost Ranch as it appears in 2019.
Skull diagram with elongated teeth (according to Nesbitt & Sues, 2020) [ 2 ]